//////////////////////license & copyright header/////////////////////////
//                                                                     //
//    Base64 - encode/decode data using the Base64 encoding scheme     //
//                                                                     //
//                Copyright (c) 1998 by Kevin Kelley                   //
//                                                                     //
// This library is free software; you can redistribute it and/or       //
// modify it under the terms of the GNU Lesser General Public          //
// License as published by the Free Software Foundation; either        //
// version 2.1 of the License, or (at your option) any later version.  //
//                                                                     //
// This library is distributed in the hope that it will be useful,     //
// but WITHOUT ANY WARRANTY; without even the implied warranty of      //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the       //
// GNU Lesser General Public License for more details.                 //
//                                                                     //
// You should have received a copy of the GNU Lesser General Public    //
// License along with this library; if not, write to the Free Software //
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA           //
// 02111-1307, USA, or contact the author:                             //
//                                                                     //
// Kevin Kelley <kelley@ruralnet.net> - 30718 Rd. 28, La Junta, CO,    //
// 81050  USA.                                                         //
//                                                                     //
////////////////////end license & copyright header///////////////////////

package org.objectweb.jac.util;

import java.io.*;       // needed only for main() method.


/**
 * Provides encoding of raw bytes to base64-encoded characters, and
 * decoding of base64 characters to raw bytes.
 *
 * @author Kevin Kelley (kelley@ruralnet.net)
 * @version 1.3
 */
public class Base64 {

   /**
    * returns an array of base64-encoded characters to represent the
    * passed data array.
    *
    * @param data the array of bytes to encode
    * @return base64-coded character array.
    */
   static public char[] encode(byte[] data)
   {
      char[] out = new char[((data.length + 2) / 3) * 4];

      //
      // 3 bytes encode to 4 chars.  Output is always an even
      // multiple of 4 characters.
      //
      for (int i=0, index=0; i<data.length; i+=3, index+=4) {
         boolean quad = false;
         boolean trip = false;

         int val = (0xFF & (int) data[i]);
         val <<= 8;
         if ((i+1) < data.length) {
            val |= (0xFF & (int) data[i+1]);
            trip = true;
         }
         val <<= 8;
         if ((i+2) < data.length) {
            val |= (0xFF & (int) data[i+2]);
            quad = true;
         }
         out[index+3] = alphabet[(quad? (val & 0x3F): 64)];
         val >>= 6;
         out[index+2] = alphabet[(trip? (val & 0x3F): 64)];
         val >>= 6;
         out[index+1] = alphabet[val & 0x3F];
         val >>= 6;
         out[index+0] = alphabet[val & 0x3F];
      }
      return out;
   }

   public static String encodeToString(byte[] data) {
      return new String(encode(data));
   }

   /**
    * Decodes a BASE-64 encoded stream to recover the original
    * data. White space before and after will be trimmed away,
    * but no other manipulation of the input will be performed.
    *
    * As of version 1.2 this method will properly handle input
    * containing junk characters (newlines and the like) rather
    * than throwing an error. It does this by pre-parsing the
    * input and generating from that a count of VALID input
    * characters.
    **/
   static public byte[] decode(char[] data)
   {
      // as our input could contain non-BASE64 data (newlines,
      // whitespace of any sort, whatever) we must first adjust
      // our count of USABLE data so that...
      // (a) we don't misallocate the output array, and
      // (b) think that we miscalculated our data length
      //     just because of extraneous throw-away junk

      int tempLen = data.length;
      for( int ix=0; ix<data.length; ix++ )
      {
         if( (data[ix] > 255) || codes[ data[ix] ] < 0 )
            --tempLen;  // ignore non-valid chars and padding
      }
      // calculate required length:
      //  -- 3 bytes for every 4 valid base64 chars
      //  -- plus 2 bytes if there are 3 extra base64 chars,
      //     or plus 1 byte if there are 2 extra.

      int len = (tempLen / 4) * 3;
      if ((tempLen % 4) == 3) len += 2;
      if ((tempLen % 4) == 2) len += 1;

      byte[] out = new byte[len];



      int shift = 0;   // # of excess bits stored in accum
      int accum = 0;   // excess bits
      int index = 0;

      // we now go through the entire array (NOT using the 'tempLen' value)
      for (int ix=0; ix<data.length; ix++)
      {
         int value = (data[ix]>255)? -1: codes[ data[ix] ];

         if ( value >= 0 )           // skip over non-code
         {
            accum <<= 6;            // bits shift up by 6 each time thru
            shift += 6;             // loop, with new bits being put in
            accum |= value;         // at the bottom.
            if ( shift >= 8 )       // whenever there are 8 or more shifted in,
            {
               shift -= 8;         // write them out (from the top, leaving any
               out[index++] =      // excess at the bottom for next iteration.
                  (byte) ((accum >> shift) & 0xff);
            }
         }
         // we will also have skipped processing a padding null byte ('=') here;
         // these are used ONLY for padding to an even length and do not legally
         // occur as encoded data. for this reason we can ignore the fact that
         // no index++ operation occurs in that special case: the out[] array is
         // initialized to all-zero bytes to start with and that works to our
         // advantage in this combination.
      }

      // if there is STILL something wrong we just have to throw up now!
      if( index != out.length)
      {
         throw new Error("Miscalculated data length (wrote " + index + " instead of " + out.length + ")");
      }

      return out;
   }

   public static byte[] decode(String data) {
      return decode(data.toCharArray());
   }

   //
   // code characters for values 0..63
   //
   static private char[] alphabet =
   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
   .toCharArray();

   //
   // lookup table for converting base64 characters to value in range 0..63
   //
   static private byte[] codes = new byte[256];
   static {
      for (int i=0; i<256; i++) codes[i] = -1;
      for (int i = 'A'; i <= 'Z'; i++) codes[i] = (byte)(     i - 'A');
      for (int i = 'a'; i <= 'z'; i++) codes[i] = (byte)(26 + i - 'a');
      for (int i = '0'; i <= '9'; i++) codes[i] = (byte)(52 + i - '0');
      codes['+'] = 62;
      codes['/'] = 63;
   }




   ///////////////////////////////////////////////////
   // remainder (main method and helper functions) is
   // for testing purposes only, feel free to clip it.
   ///////////////////////////////////////////////////

   public static void main(String[] args)
   {
      boolean decode = false;

      if (args.length == 0) {
         System.out.println("usage:  java Base64 [-d[ecode]] filename");
         System.exit(0);
      }
      for (int i=0; i<args.length; i++) {
         if ("-decode".equalsIgnoreCase(args[i])) decode = true;
         else if ("-d".equalsIgnoreCase(args[i])) decode = true;
      }

      String filename = args[args.length-1];
      File file = new File(filename);
      if (!file.exists()) {
         System.out.println("Error:  file '" + filename + "' doesn't exist!");
         System.exit(0);
      }

      if (decode)
      {
         char[] encoded = readChars(file);
         byte[] decoded = decode(encoded);
         writeBytes(file, decoded);
      }
      else
      {
         byte[] decoded = readBytes(file);
         char[] encoded = encode(decoded);
         writeChars(file, encoded);
      }
   }

   private static byte[] readBytes(File file)
   {
      ByteArrayOutputStream baos = new ByteArrayOutputStream();
      try
      {
         InputStream fis = new FileInputStream(file);
         InputStream is = new BufferedInputStream(fis);
         int count = 0;
         byte[] buf = new byte[16384];
         while ((count=is.read(buf)) != -1) {
            if (count > 0) baos.write(buf, 0, count);
         }
         is.close();
      }
      catch (Exception e) { e.printStackTrace(); }

      return baos.toByteArray();
   }

   private static char[] readChars(File file)
   {
      CharArrayWriter caw = new CharArrayWriter();
      try
      {
         Reader fr = new FileReader(file);
         Reader in = new BufferedReader(fr);
         int count = 0;
         char[] buf = new char[16384];
         while ((count=in.read(buf)) != -1) {
            if (count > 0) caw.write(buf, 0, count);
         }
         in.close();
      }
      catch (Exception e) { e.printStackTrace(); }

      return caw.toCharArray();
   }

   private static void writeBytes(File file, byte[] data) {
      try {
         OutputStream fos = new FileOutputStream(file);
         OutputStream os = new BufferedOutputStream(fos);
         os.write(data);
         os.close();
      }
      catch (Exception e) { e.printStackTrace(); }
   }

   private static void writeChars(File file, char[] data) {
      try {
         Writer fos = new FileWriter(file);
         Writer os = new BufferedWriter(fos);
         os.write(data);
         os.close();
      }
      catch (Exception e) { e.printStackTrace(); }
   }
   ///////////////////////////////////////////////////
   // end of test code.
   ///////////////////////////////////////////////////

}
